It is common to use lamps with rechargeable power packs because of their dependability and low maintenance cost. Such lamps have many industrial applications, such as in underground work in mines, tunnels and the like. Quite often the lamp is secured to the helmet of the user and the power pack is secured to the user's waist. Electrical wiring delivers power from the power pack to the lamp on the helmet. Normally at the end of each working shift, the lamp and power pack are removed and placed in a recharging device, so that the power pack is ready for reuse at the next working shift.
An example of this type of lamp is disclosed in U.S. Pat. No. 2,312,614. The power pack includes a plurality of batteries which are rechargeable. Electrical wiring connects a lamp which is securable to the worker's helmet to the batteries. The batteries are normally the wet cell, lead acid storage battery type which include appropriate venting devices to prevent electrolyte spillage. However, some electrolyte leakage can occur where the leaked acid damages the user's clothes and skin.
The power pack is charged by either using the lamp, which has appropriate electrodes for connection to a charging circuit, or connecting the battery to a charging circuit. In this U.S. patent, examples of both techniques are disclosed. In recharging the battery, it is important that it be positioned upright to provide proper venting of the battery during charging and to preclude electrolyte spillage. Recharging of the battery by use of the lamp is also disclosed in U.S. Pat. No. 2,066,811. Electrodes are positioned at the base of the lamp which are to a recharging circuit. By appropriately adjusting the control switch, the battery may be recharged during non-use. However, such arrangement requires the user to properly adjust the switch at the end of the shift and insert the lamp in the recharging device.
Insofar as recharging the battery where electrodes are positioned on the battery, an example is disclosed in U.S. Pat. No. 4,207,660. In this arrangement, several electrodes are positioned on the battery where at least two of the electrodes will form electrical contact with the recharging circuit to recharge the battery. Another example of external electrodes on the battery for purposes of recharging is in U.S. Pat. No. 4,317,162. The battery construction has the common lead acid arrangement with positive and negative charging terminals on the battery exterior. Because of the use of lead acid storage batteries, the unit must be retained in the upright position for purposes of recharging to prevent electrolyte spillage.
The use of nickel-cadmium batteries have become very popular because they are dry cell, hold their charge, have good discharge characteristics and are readily rechargeable. However, in the lamp field particularly for use in mining and the like, nickel-cadmium batteries are not that extensively used. Instead the lead acid form of batteries is by far the most popular.